A vast majority of diagnostics for reciprocating compressors require data about the mechanical top-dead-center (TDC) position of the compressing piston inside the compressor's cylinder. Other data about the reciprocating compressor is indexed to the TDC position data. Conventional diagnostic approaches for determining this TDC position on a reciprocating compressor require that the compressor be powered off (shutdown). With the compressor shut down, a dial indicator or level may be used to determine the TDC position. With the TDC established, a proximity probe may be installed to view an event on the crankshaft or crosshead. The structure(s) viewed by the proximity probe may be detectable on a once-per-turn or multiple-event-per-turn basis, or a combination thereof. After determining the TDC position and installing the proximity probe, the compressor maybe re-started. The conventional approach relies upon this proximity probe and an event (referred to as a phase-reference transducer) along with requisite wiring connecting the probe and the transducer, to mark TDC for each revolution. Modification of the compressor and/or crankshaft, installation of wiring, and verification of components add expense to the diagnostic system.
Additionally, in conventional approaches, the event data must be collected simultaneously across the pressure transducer and the phase-reference transducer so that the TDC marked by the phase-reference transducer can be accurately related to the pressure transducer. The need for this type of simultaneous data collection nearly excludes wireless transmission of data from the compressor as it can be difficult to ensure simultaneous transmission of data from various points, particularly in industrial environments.
Prior example approaches for determining the TDC of a reciprocating engine include comparing measured event data to a thermodynamic model or comparing measured event data to a model pressure curve ratio. In both cases, the models include pre-supposed information about the engine, and building those models requires additional time and resources, e.g., for development and tuning.